SANTA ROSA, Calif. — More than 1,000 people marched Tuesday to protest the fatal shooting of a 13-year-old boy by a Northern California sheriff’s deputy in an encounter that sparked community outrage and an FBI investigation.

Officers stood on rooftops and others wearing helmets stood guard at barricades that kept the protesters away from the Sonoma County Sheriff’s Office in Santa Rosa.

The protesters, including middle- and high-school-age students and members of the Occupy Oakland movement, assembled in downtown Santa Rosa before marching through streets with signs and hooded sweatshirts bearing photos of the boy.

“Andy Lopez did not have to die,” they chanted during the nearly three-hour, mostly peaceful demonstration. No arrests were made.

Lopez was shot and killed Oct. 22 by Sonoma County Deputy Erick Gelhaus, a firearms instructor who authorities said mistook a pellet gun carried by Lopez for an assault rifle.

Investigators say the hoodie-wearing teen didn’t comply with commands to drop the gun and was turning toward deputies while raising the barrel when he was shot multiple times.

The incident remained under investigation by the FBI, Sonoma County prosecutors and Santa Rosa police.

Victor Manieri, 15, a freshman at Elsie Allen High School, left school early to join the march. He said he knew Andy and wanted to show support for his family.

“I disagree with what that cop did that day,” Manieri said. “There are other methods such as using a Taser that would paralyze him, not take away his life.”

Mitzi Reyes, 16, a junior at Elsie Allen, marched with her mother and two younger brothers. They also knew Andy and his family.

“I’m here today because I want to get justice not only for Andy but for other people that have died for no reason,” she said.

The shooting has generated several protests in Santa Rosa, located about 50 miles northwest of San Francisco. On Sunday, more than 1,000 people turned out for a service to remember Lopez.

Sonoma County Assistant Sheriff Lorenzo Duenas said Gelhaus, 48, has been a Sonoma County firearms instructor and rangemaster for 19 years and has trained his law enforcement colleagues in the use of force. He is one of 26 such instructors for the county.

Gelhaus also teaches pistol, carbine, shotgun and rifle lessons for Gunsite, a private company in Arizona, according to the company’s website.